The present invention relates to a novel direct drawing type lithographic printing plate precursor and a method for producing a lithographic printing plate using the same, and more specifically to a method for producing a lithographic printing plate using oil-based ink for ink jet recording and superior in plate-making quality and printed image quality.
With the development of office appliances and the expansion of office automation in recent years, it has been prevalent in the field of small-scale printing to adopt an offset printing system utilizing various means for plate-making, i.e., for image-forming on a direct drawing type lithographic printing plate precursor having an image-receiving layer provided on a water-resisting support to thereby produce a printing plate.
Conventional direct drawing type lithographic printing plate precursors comprise a water-resisting support having provided thereon an image-receiving layer, and a lipophilic image is formed on such a direct drawing type lithographic printing plate precursor with oil-based ink by means of a typewriter or handwriting, or a lipophilic image is formed by heat-fusion transferring an image from an ink ribbon with a heat transfer printer and, if necessary, performing hydrophilization treatment of a non-image area, to thereby obtain a printing plate.
However, since the printing plate produced by this method is insufficient in mechanical strength of the image area, peeling off of the image area may occur during printing.
Further, plate-making of the above-described direct drawing type lithographic printing plate precursor by an ink jet printer is performed, wherein water base ink with water as a dispersion medium is used, but this technique has a drawback in that the water base ink oozes from the image on the printing plate and the drawing rate lowers since it takes time to dry the ink. To alleviate this problem, a method of using oil-based ink where a non-water base dispersion medium is used is disclosed in JP-A-54-117203 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d).
However, since the ink is ejected from a thin nozzle in this method, clogging may occur at the discharge part.
The present invention has been completed to solve the above-described problems and an object of the present invention is to provide a direct drawing type lithographic printing plate precursor capable of providing a large number of prints having clear images.
Other objects and effects of the present invention will become apparent from the following description.
The above objects of the present invention have been achieved by providing the following lithographic printing plate precursors (1) to (8) and printing plate preparation method (9).
(1) A direct drawing lithographic printing plate precursor, which comprises a water-resisting support having provided thereon an image-receiving layer, an image being formed on the image-receiving layer with an oil-based ink by an electrostatic ink jet system,
wherein said water-resisting support has at least a resin coating layer on the side opposite to the side on which the image-receiving layer is provided,
wherein said resin coating layer comprises a mixture containing from 10 to 90 wt % of a low density polyethylene having a density of from 0.95 to 0.930 g/ml and a melt index of from 1.0 to 30.0 g/10 min., and from 10 to 90 wt % of a high density polyethylene having a density of from 0.940 to 0.970 g/ml and a melt index of from 1.0 to 30.0 g/10 min.,
wherein the surface of said resin coating layer has a Bekk""s smoothness of from 5 to 2,000 sec/10 ml, and
wherein said water-resisting support has a conductive layer having a specific electric resistance value of 1010 xcexa9xc2x7cm or less on the image-receiving layer side surface thereof and on at least one end face thereof.
(2) The direct drawing lithographic printing plate precursor according to the above (1), wherein said image-receiving layer is formed from a dispersion comprising:
an inorganic pigment comprising silica particles having an average particle diameter of from 1 to 6 xcexcm and ultra-fine particles of inorganic pigment having an average particle diameter of from 5 to 50 nm, at a weight ratio of from 40/60 to 70/30; and
at least one hydrophilic resin modified with a silyl functional group represented by the following formula (I):
xe2x80x94Si(R)n(OX)3xe2x88x92nxe2x80x83xe2x80x83(I)
xe2x80x83wherein R represents a hydrogen atom or a hydrocarbon group having from 1 to 12 carbon atoms; X represents an aliphatic group having from 1 to 12 carbon atoms; and n represents 0, 1 or 2.
(3) The direct drawing lithographic printing plate precursor according to the above (2), wherein said dispersion further contains gelatin and a gelatin-hardening compound.
(4) The direct drawing lithographic printing plate precursor according to the above (2), wherein the colloidal ultra-fine particles of inorganic pigment having an average particle diameter of from 5 to 50 nm comprise at least one member selected from colloidal silica, titania sol and alumina sol.
(5) The direct drawing lithographic printing plate precursor according to the above (3), wherein the gelatin-hardening compound is a compound having in its molecule at least two double bond groups represented by the following formula (II):
CH2xe2x95x90CHxe2x80x94Wxe2x80x94xe2x80x83xe2x80x83(II)
wherein W represents xe2x80x94OSO2xe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94CONR1xe2x80x94 or xe2x80x94SO2NR1xe2x80x94 (wherein R1 represents a hydrogen atom or an aliphatic group having from 1 to 8 carbon atoms).
(6) The direct drawing lithographic printing plate precursor according to the above (1), wherein said image-receiving layer contains:
at least one kind of particles having an average particle diameter of from 0.01 to 5 xcexcm and comprising atoms having interatomic ionic bonding rate of Pauling of the compound of 0.2 or more, which particle being selected from hydrous metallic compounds, metallic oxides and double oxides; and
a binder resin containing a complex comprising: a resin having a siloxane bond connected with Si via an oxygen atom; and an organic polymer containing a group capable of bonding with said resin via hydrogen bonding.
(7) The direct drawing lithographic printing plate precursor according to the above (6), wherein said resin containing siloxane bond is a polymer obtained by hydrolysis polycondensation of at least one silane compound represented by the following formula (III):
(R0)mSi(Y)4xe2x88x92mxe2x80x83xe2x80x83(III)
wherein R0 represents a hydrogen atom, a hydrocarbon group or a heterocyclic group; Y represents a hydrogen atom, a halogen atom, xe2x80x94OR2, xe2x80x94OCOR3, or xe2x80x94N(R4)(R5) (wherein R2 and R3 each represents a hydrocarbon group, and R4 and R5, which may be the same or different, each represents a hydrogen atom or a hydrocarbon group); and m represents 0, 1 or 2, provided that the case in which Si atom is bonded to three hydrogen atoms is excluded.
(8) The direct drawing lithographic printing plate precursor according to the above (1), wherein said image-receiving layer has a surface smoothness of 30 sec/10 ml or more in terms of Bekk""s smoothness.
(9) A method for preparing a direct drawing lithographic printing plate, which comprises:
ejecting an oil-based ink by an electrostatic ink jet recording system onto an image-receiving layer of a direct drawing lithographic printing plate precursor according to the above (1) to form an image thereon,
wherein said oil-based ink is a dispersion comprising:
a non-aqueous solvent having an electric resistance of 109 xcexa9xc2x7cm or more and a dielectric constant of 3.5 or less as a dispersion medium; and
hydrophobic charged resin particles, which are solid at least at normal temperature, dispersed in the non-aqueous solvent.